top of page

Ep64 – The Micronutrients Series: Fat Soluble Vitamins Part 2 (Vitamin D)

Updated: Oct 27, 2023


Hello, you are listening to Katy Bradbury, registered nurse and nutrition therapist. Today’s podcast episode is called The Micronutrients Series Fat Soluble Vitamins Part 2.


So in today’s episode, I am continuing to talk to you about micronutrients. So, over the next few weeks, I will be covering the full spectrum of vitamins and minerals that are associated with fertility for lots of different for lots of different reasons. And I just thought it might be a nice idea, as I explained last week, to go through these micronutrients in a bit more detail and give a spotlight to each and every one of them. And that’s not to say that we should get fixated on any particular one of these micronutrients. It’s more just to aid your understanding of why a varied diet, a nutritious diet that is full of different plant foods and all the different colours of the rainbow. And a varied diet generally, because it’s not all just plant foods, is really, really important for fertility. So without further ado, I’m going to talk to you about vitamin D today.


Vitamin D is a really well known micronutrient; it’s a really well known vitamin when it comes to fertility. And this is one that actually fertility clinics will often test. And if it’s found that your vitamin D levels are subpar, then it may be that you need to go away and improve those levels before you have your fertility treatment. And that’s because there’s a wide body of evidence now that talks about this. So I’m going to talk to you today about what vitamin D is and what it does in the body. I’m going to give a brief review of some of the evidence in relation to fertility. And we’re going to talk about things that can impact our vitamin D status and how we can improve it. So vitamin D, as I started last week with vitamin A, so I’m currently running through the fat soluble vitamins. So vitamin D is one of the fat soluble vitamins. That means that it needs adequate fat to be able to be absorbed and utilised. So unlike water soluble, which are water soluble, the fat soluble vitamins need adequate fats. So if you have an issue with either not having the right kind of fats in your diet or not absorbing your fats very well, then it may be that your vitamin D levels are depleted.


So vitamin D for fertility. So the role of vitamin D in general, so probably most of you are aware that vitamin D is the sunshine vitamin, right? We are able as humans to synthesise our own vitamin D via the skin using sunlight using UVB rays. So once the UVB rays hit our skin, we are then able to synthesise vitamin D and use that vitamin D. There is some vitamin D in some foods, but you couldn’t really get enough vitamin D from diet alone. It’s not just about the foods you eat. We do need that sunshine to help us along.


So vitamin D is really important when we’re thinking about bone health because it helps us absorb calcium, so it’s like a bit of a lock and key mechanism in our ability to absorb calcium. The reason that’s really important in terms of hormones and fertility is because it is really important for foetal development, right so you got to actually be able to produce the bones that will be the skeletal structure for your baby. We need to have enough vitamin D. It’s also really important in those early years of rapid rowth, rapid rowth! Of rapid growth in childhood development. So it’s a really important one for children and adults alike. And when we’re thinking about the ageing process and getting older, we know that vitamin D is really important for bone health and preventing osteoporosis and these kinds of things. So really important actually across the whole lifespan.


Vitamin D is immune modulating, so it supports the immune system. And it really got quite a name for itself over the last few years in relation to the COVID pandemic. There was lots and lots of stuff coming out about how important vitamin D was in its role in our immunity and about it possibly having a protective factor against the severity of COVID. It’s also important in the context of autoimmunity. So it is thought to be immune modulating and so having a good vitamin D status is really important in the context of autoimmunity as well. Lots of the clients that I have come to see me do have autoimmunity, more often than not with the thyroid, but in other parts of the body as well. Blood sugar regulation and metabolism generally. So vitamin D does have a really important role to play is thought to be, so people who have obesity and diabetes etc., are thought to have lower vitamin D status. And then, it is also thought to have a key role in sex hormone synthesis. So sex hormones, male and female, need vitamin E tut vitamin D to be able to produce properly. And we do also know that all of our reproductive organs, all of our reproductive tissues, male and female, have vitamin D receptors within them. And that goes to show that vitamin D must be really important within those reproductive organs. Otherwise, they wouldn’t have vitamin D receptors.


So lots of different things, lots of different roles that Vitamin D plays in the body. And within the context of fertility alone, there’s been a lot of research into vitamin D. It is one of the biggest and most well researched vitamins that there is actually, and it’s almost vitamin D is almost ought to have a hormonal effect because a hormone is a chemical messenger, and vitamin D, such as the importance of vitamin D. That is, it is akin to being a hormone in of its own right.


So vitamin D and fertility. So there have been a number of systematic reviews and meta analyses. So these are really, you know, there’s really widespread data available in this in the scientific literature, you know, looking at certain samples of 1000s of 1000s of people. So, findings from the research suggest that it’s, it’s mainly looking, by the way, the research mainly looks at vitamin D status. So there haven’t been that many randomised control trials where there’s been an intervention of a certain dose of vitamin D being given versus a control group where the vitamin D isn’t given to see whether that might impact things. And part of the reason that I think randomise, sorry, yep, randomised controlled trials aren’t necessarily, ran RCTs randomised controlled trials are seen as the gold standard when it comes to medical research when it comes to scientific research in general. However, they do have their drawbacks. In this, in a case like vitamin D, I think it’s more powerful, too. And we could of course, association does not always equal causation. But what we’re seeing time and time and time again in the literature is that vitamin D status, so people who have low levels of serum vitamin D, so low levels of Vitamin D in their blood are more likely to have this whole host of complications with fertility complications with pregnancy complications with their health in general. So that really speaks volumes. And where it becomes difficult to say, Okay, well, let’s then do a randomised control trial is because all sorts of things can impact people’s vitamin D status. And the dosages are going to look different for everyone. So I don’t know that we can necessarily say, Okay, well, guess if we supplement everyone with this amount of vitamin D, then we’re going to solve all the fertility problems in the world because it’s just not that simple in bodies and more complex than that. But what we do know, as I say, to come back to my original point about the research, is that these observational studies on 1000s and 1000s of women do say that people who are women who have deficient or insufficient vitamin D status are more likely to have or sorry. So women who have insufficient levels compared with women who have good levels of vitamin D in the blood. So, women with good levels, or replete levels of vitamin D is quite a nice way of putting it, have more live births, more positive pregnancy tests, and more clinical pregnancies. So that’s really interesting. Across fertility clinics, all of those measures are higher in women who had adequate vitamin D levels. And there’s been lots and lots of research that has found similar. There has been some research to say that women who have really quite a low vitamin D below 50 nanomoles per litre might be more likely to suffer from early pregnancy loss.


There are some studies that observe an association between vitamin D status and AMH Anti-Müllerian Hormone, which is one of the indicators of egg reserve. Vitamin D status is also connected with conditions medical conditions that we know impact fertility, such as polycystic ovary syndrome, PCOS, and endometriosis. So, really lots of lots of ways in which vitamin D impacts female fertility or is associated with female fertility. And then there is also research now quite a bit of research associating vitamin D again, vitamin D, low vitamin D levels, with low serum testosterone, for men, and in their sperm quality as well.


So that is really interesting, isn’t it, that across the male and female spectrum of fertility, vitamin D status is associated quite strongly and quite robustly with poor outcomes in terms of or good outcomes depending on the status for fertility. So undeniably a really important nutrient for fertility or a really important vitamin for fertility, I should say, because we don’t always get it from our food.


So things that can impact vitamin D status, like why might someone’s vitamin D status be low? Well, we know that it can be used for all sorts of things in the body, as I already described. So it may be that at different points in our lifespan, we use up more vitamin D than others. Things such as our genetics play a role. So we have a gene called the vitamin D receptor gene, the VDR gene, and that is involved in the methylation process, which I’ve spoken about on the podcast before. And it really is the vitamin D receptor gene, having a genetic variant on that gene that can really impact the way our vitamin D is actually used in the body. But other genes as well. It’s not just the vitamin D receptor gene. It can be genes that are linked with our cholesterol status. And a number of other genes can have a proxy impact on vitamin D as well.


Lack of sunlight, so we know you know that we get vitamin D from the sun or we synthesise vitamin D from the sun. So having a lack of sunlight, particularly during the autumn months, if you live in the, you know, away, the further away from the equator you live, the less hours of sunlight you get during the autumn and winter months, and that can impact your vitamin D status. Another interesting piece of research around fertility, you know, suggested that the fact that most babies are born in the northern hemisphere, or you know, in the north, in the northern countries, most babies are born, or there’s a drive for births when people got pregnant, basically during the summer, the summer months. So how many April babies do you know, for example, April is a really popular month for having babies, and it’s hypothesised that vitamin D might have something to do with that. So, exposure to sunlight, the genetics.


So sunscreen, sunscreen blocks UV rays, right, that’s how it protects our skin. And I’m not for a moment suggesting that anyone any of you go out all day in the sun unprotected because, of course, we need to protect our skin because we know that the sun’s rays can be extremely harmful. So it’s right that we protect our skin. However, if we, you know, if we put some cream on from before we even leave the house, and we reapply it all day long, and we never ever actually get any direct sunlight on our skin, then that can impact our vitamin D status. So I always say to people, you know, doing sort of 10 minutes or so, in the morning before the heat of the day can be a really nice idea.


Age, so there is an age related decline in vitamin D status, and mineral status can impact it. So magnesium levels are thought to be associated inversely with vitamin D. Skin colour as well. So people, essentially humans, evolved. So, historically speaking, as we moved out of Africa and away from the equator, human beings’ skin got lighter and lighter. And that is thought to be because there was then an evolutionary what’s the word I’m looking for selective pressure on us because we because there were fewer hours of sunlight or less powerful sunlight the further away we got from the equator. That is why we have evolved lighter skin tones. And if you think of people from like Scandinavian countries, where there is really not a huge amount of daylight in the winter months, you know, they tend to have much paler skin tones, don’t they? They’re very, very fair. And a part of that is to help them actually absorb and synthesise vitamin D. So what that means is that people who have darker skin tones, especially people who have darker skin tones who don’t live in equatorial or within the tropics and have don’t have that quite into that higher intensity of sunlight, they may be more likely to to be deficient or insufficient in vitamin D. So skin colour, sunscreen, age, mineral status, oh and fat absorption.


Fat absorption. I spoke about this last time in my introduction to this mini-series that our ability to absorb fats as a macronutrient impacts our ability to absorb and utilise the fat soluble vitamins.


So food sources vitamin D, and this is an interesting one because there aren’t that many. And as I said earlier, you can’t really get enough vitamin D from food alone. There are a few foods that contain some vitamin D, with salmon being the highest. Sardines contain some, and tuna contain some. Pasture-raised cow’s milk also does contain a little, eggs contain a little, and shiitake mushrooms contain a tiny amount as well. So definitely think about those kinds of foods if you are concerned about your vitamin D, but do know that lots of people do need to supplement.


So when I’m working with fertility clients, I always test vitamin D, and I like to see vitamin D serum vitamin D levels are between 100 and 120 nanomoles per litre. So that unit is really important because, for any of my American listeners or any listeners anywhere else in the globe, you may use different units. So I know over in the states, they use nanograms per millilitre, and that is different to nanomoles per litre. So please make sure that you’re aware of that distinction. So I look for 120 nanomoles per litre for my fertility clients. And if people are below that, then I might consider supplementing and indeed Public Health England, because if the vitamin D insufficiency is deemed a public health crisis in the Northern Hemisphere, the Public Health England recommends that everyone, everyone in the UK take 400 international units of vitamin D between the months of October to March. So that’s, that’s universal. But levels that I might recommend supplementing with really vary between 400 and 5,000 international units per day, sometimes even a little bit more on certain days of the week for certain people, but it really really does depend on the individual. So I would never recommend that any listeners ever go away and decide to supplement themselves without the guidance of a qualified practitioner because it really does depend on the individual. However, you know, if you are following the Public Health England guidance and supplementing with your 400 international units per day during those autumn and winter months, then please do look for D3, vitamin D3, as opposed to vitamin D2. It’s far more readily absorbed, and your body does not have to undergo a conversion process. So when you’re looking for a vitamin D supplement, please go for D3 over D2.


So that’s it for me today. That’s a whistlestop tour with the spotlight on vitamin D in the context of fertility, pregnancy etc. So if you found that useful for anyone that noticed, and you might have noticed that I am a day late and recording the podcast today. The reason for that is purely that I was bloody knackered last night because we had a wonderful long bank holiday weekend here in the UK with the Queen’s Jubilee. So we had a four day weekend, and it also happened to be my mom’s birthday and my husband’s birthday. So we had family visiting, and we had a bit of a party, so it was all go. I came to record my podcast yesterday, and I was just too tired, so so I’m recording it on a Monday today. I will be back as usual next week talking about the remaining fat soluble vitamins E and K in relation to fertility, so I really can’t wait to speak to you then.


Just a quick reminder that the doors are currently open to my brand new membership. We had the first call last week, and it was so so wonderful to connect with the most incredible group of people again. And I’m really, really excited to be opening up this group way of working again is so nurturing and so powerful. So if that sounds like it could be helpful for you, please do take a look. There are just a couple more slots in the cheaper price bracket, the introductory price bracket of £50 a month. So it is an incredible, incredible value deal. If you want to come in and join us that you know there is, you can cancel at any time. But I don’t think you’ll want to once you get a taste of what it’s like in there because it genuinely is such a wonderful, wonderful space. So I will leave the link to that in the show notes for anyone that wants to take a look, get all the information, and you can sign up on the spot. Or if you have any questions for me about the contents of today’s show or about anything, or you want to talk about how ways in which you can work with me, whether that’s one to one or in a group setting. Then drop me a DM on Instagram is usually best at KatyBradburyHealth, or you can always send me an email at


All right, lovely to chat with you. And I will speak to you again next week. Bye

Linked mention in the podcast

You can connect with me in the following ways:

5 views0 comments

Recent Posts

See All


bottom of page